摘要:

Adenosine-modified glassy carbon electrodes were prepared for the determination of glucose without using an immobilized redox mediator. Glucose oxidase (GOD) was immobilized with Nafion film onto an adenosine-modified electrode, which could electrochemically oxidize the immobilized GOD by differential pulse voltammetry at a peak potential of -470 mV vs. SCE. The peak can be used in the analysis of the substrate, although from the response of the GOD electrode it is not clear whether the redox centers from the GOD are dissociated completely or partially. The increase of the peak current with the concentration of glucose shows that the adenosine-modified electrode can be used for the determination of glucose. The enzymatic activity of GOD immobilized on the adenosine-modified electrode was greatly influenced by the length of electrode surface oxidation. The apparent Michaelis constant,Km' and the current maximum,Imax, obtained from Lineweaver-Burk plot of the calibration curve were 33 mM and 1.9 mA respectively (r = 0.998, n = 6).

ISSN:0003-2719    

DOI:10.1080/00032719708001714

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new amperometric turnip tissue-based hydrogen peroxide biosensor has been developed. The detection principle of H2O2involves the mediation by ferrocene which has been premixed with the turnip tissue in a carbon paste matrix. Due to the intimate contact between the biocatalytic and sensing sites, a very fast steady state response for the H2O2detection has been obtained. The linear calibration range is 0.06 to 0.85 mM with a correlation of 0.998. The sensitivity of the biosensor decreased by less than 2% after 1 week of continuous use.

ISSN:0003-2719    

DOI:10.1080/00032719708001715

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The construction and general performance characteristics of potentiometric plastic-membrane sensors for enalapril and ramipril drug-anions, are described. The electroactive materials are based on ion pair complexes between enalapril and ramipril anions, respectively, with Aliquot 336S cation. Both electrodes show near Nerstian response over the range 1 × 10−2- 10−5mol/L, with a detection limit of about 2.4 × 10−6mol/L for enalapril and 6 × 10−6mol/L for ramipril. The selectivity of the electrodes to a number of organic and norganic anions is reported. The electrodes proved useful in the determination of the active ingredient in their respective pharmaceutical preparations. The method is simple, rapid and does not require prior sample pre-treatment.

ISSN:0003-2719    

DOI:10.1080/00032719708001716

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The anticancer agent CAI was quantitated from human plasma using a C-18 column with a mobile phase consisting of acetonitrile and water (each containing 0.01M ammonium acetate) pumped over a gradient at a flow rate of 1.0 mL min. The detection of CAI and the internal standard, harmine, was accomplished using a photodiode-array detector set at 264 and 323 nm, respectively. The chromatographic run time was 17.5 minutes. The plasma samples were prepared for HPLC analysis using a C-18 solid phase extraction procedure. Two calibration curves were prepared. and the assay was shown to be linear in the concentration range of 0.02 to 0.5 μg/mL for the low curve and 0.25 to 10.0 μg/mL for the high curve, with average correlation coefficients of 0.9933 and 0.9938, respectively. Intra-assay and inter-assay imprecisions were less than 10.0% with an error of accuracy of less than 11.0%. The assay was reproducible with the sensitivity needed for the prediction of CAI levels in the plasma of cancer patients.

ISSN:0003-2719    

DOI:10.1080/00032719708001717

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This report deals with the application of cyclic voltammetry for the preparation of polymer modified electrodes. The monomer used was diphenyl amine (DPA), and the electrolyte was HClO4. Cyclic voltammetry was used because the polymer formed by this method adheres tightly to the electrode and also deposits as a very smooth layer. The polymer was then used on the glassy carbon electrode in order to make a modified electrode for detection of vitamin C in urine. Different variables were studied in order to find the most suitable conditions for this electrode. Linear response of electrode to ascorbic acid concentration was very high with limit of detection of 0.2 ppm.

ISSN:0003-2719    

DOI:10.1080/00032719708001718

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two simple, rapid specific methods were developed for the determination of heptaminol and mexiletine and their dosage forms. The methods are based on the reaction of either heptaminol or mexiletine with acetylacetone-formaldehyde reagent to give a yellow chromophore measurable spectrophotometrically at 344 or 338 nm or flurometrically at 480 nm for heptaminol and mexiletine, respectively. The color was stable for at least 1/2 h. Beer's law was valid within a concentration range of 15–30 and 8–20 μg ml−1spectrophotometrically and 0.2–0.8 and 0.4–1.0 μg ml−1fluorometrically for heptaminol and mexiletine, respectively.

ISSN:0003-2719    

DOI:10.1080/00032719708001719

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Two simple and sensitive spectrophotometric procedures are suggested for analysis of triamterene. The first procedure is based on the reaction of triamterene with p-chloranilic acid (p-CA) in methylene chloride to form a highly stable coloured product, exhibiting maximum absorbance at λ 530 nm. Beer's law is obeyed in the range of 40–220 μg.ml−1with a mean percentage accuracy of 99.98 ± 0.446. Limit of determination is 20 μg.ml−1. In the second procedure, the drug is determined via charge transfer complex formation with 2,3 dichloro-5,6-dicyano p-benzoquinone (DDQ) using methylene chloride as a solvent. Here the reaction product has two well defined maxima at 460 nm and 530 nm where each has been utilized for quantitative determination. Beer's law is obeyed in concentration ranges of 25–125 μg.ml−1and 25–150 μg.ml−1with mean percentage accuracies of 99.92 ± 0.449 and 100.00 ± 0.511 for both maxima. 460 and 530 nm. respectively. Limit of determination is 12.5 μg.ml−1at both maxima. Optimum conditions for each procedure have been studied and the stoichiometry of both reactions was ascertained using Job's method of continuous variation. The validity of the suggested procedures was assessed by applying the standard addition technique using the drug capsules. Both procedures are statistically analyzed as compared with BP method for analysis of triamterene (non aqueous titration) revealing good accuracy and precision as indicated by t and F tests.

ISSN:0003-2719    

DOI:10.1080/00032719708001720

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A new method for the spectrofluorimetric determination of zinc with 1,2,4-Trihydroxyanthraquinone in a 80:20 (v/v) ethylene glycol/water medium and at an apparent pH 8.87 provided by an ammonia/ammonium chloride buffer (pH = 9.30) is proposed. The method allows the determination of zinc over the range 50–500 ng/ml and features a detection limit of 2.31 ng/ml. The influence of various chemical and physical variables affecting the reaction was evaluated and the effects of potential major interferences with the method are commented on. The proposed method has been successfully applied to the determination of zinc in several pharmaceutical preparations.

ISSN:0003-2719    

DOI:10.1080/00032719708001721

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Three spectrophotometric methods for the determination of ofloxacin and lomefloxacin hydrochloride are proposed, which are based on their extraction into chloroform as ion pairs with Bromophenol Blue (BPB), Bromothymol Blue (BTB) and Bromocresol Purple (BCP). The calibration graphs generated were linear over the range 5–25, 2–15 and 2–20 μg ml−1of drug in chloroform, using three dyes, respectively. The composition of the ion pair was established by continuous variation and molar ratio methods. The described methods were utilized for assaying ofloxacin and lomefloxacin hydrochloride in pharmaceutical preparations.

ISSN:0003-2719    

DOI:10.1080/00032719708001722

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A specific method to determine two anti-icing additives (ethylene glycol monomethylether, EGME and diethylene glycol monomethylether, DEGME) in jetfuel is described. This method is based on a gas-chromatographic technique using a mass spectrometer detector and the monitoring of selected ions (GC-MS-SIM). This specific technique has shown to be an accurate and rapid tool to carry-out these measurements in such a complex hydrocarbon matrix. The GC-MS-SIM technique, because of its specificity, does not require sample pre-treatments other than trichloroethylene (TCE) which has been selected as an internal standard. The analysis of both EGME and DEGME can be performed in less than 10 minutes in a sample of 1–5 mL. Several fuel samples were analyzed and the results compared with two standard methods.

ISSN:0003-2719    

DOI:10.1080/00032719708001723

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor